1. Field of the Invention
This invention relates to an environmental protective device for containing and recovering the effluent from a submarine oil leak at the source.
2. Description of the Prior Art
During the drilling and completion of offshore oil wells, a severe leak or so-called blowout occasionally occurs. As a result, huge quantities of oil and gas escape into the water and rise to the surface. Under action of wind and current the resulting oil slick may wash onto and contaminate beaches, fisheries and the like. Until the oil leak is brought under control, it is desirable to contain the leaking oil in situ.
Oil and gas issuing from the underwater leak is often under considerable pressure. Accordingly, the combined fluids escape as a jet. The jet action generates vortices in the water, forming a gas-saturated oil-water mixture. On reaching the surface, the gas separates from the oil-water mixture and often is ignited by a stray spark, creating a huge flare. If the oil leak issues from a ruptured underwater oil line rather than from a wellhead, little gas would issue of course, since the gas is separated from the oil before the oil is pumped into the line.
In the case of a drilling well, the drilling platform may be demolished either accidentally or purposely so that a mound of debris is strewn around the wellhead. The debris may project to a considerable height above the sea floor.
A number of containment devices are known. The containment devices are generally of two types. One style consists of a large diameter ring that floats on the water surface centered over the oil leak. Below the floating ring is suspended a barrier, usually circular, of flexible material that reaches from the surface to the sea floor around the oil leak. A toroidal or other-shaped anchor holds the barrier in place. Typical devices of the first type are exemplified by U.S. Pat. Nos. 3,653,215 to Crucet; 3,599,434 to Minaud; 3,548,605 to Paull et al, 3,879,951 to Mason; 3,469,402 to Lowd; and 4,047,390 to Boyce, II. In these devices the oil accumulates at the surface, is contained within the upper portion of the barrier and is thereafter pumped out to a storage vessel.
There are several objections to the above devices. First the lower part of the barrier must be anchored to the sea floor around the leak. Such action is difficult if not impossible in the presence of debris around the leak. Since the barrier walls are flexible, water currents, which may reach several knots, tend to distort and possibly displace the barrier walls. No provision is made to protect the device from heat if the gas becomes ignited. In most cases, the gas-saturated oil-water mixture is illustrated as being pumped out from above. Because of the high gas content, the pumps become inoperative because of vapor lock. Furthermore, in the presence of flared gas, the pumps and pipe lines and/or hoses are endangered.
Another style of oil containment device is in the form of an inverted cone or cup that is lowered over the oil leak at or near the sea floor. The leaking oil and gas is then pumped out through pipes or casing attached to the upper end of the inverted cup. These devices, too, must be anchored to the sea floor, something difficult to do in the presence of underwater obstructions. Some of the known devices provide a closed system including an oil/gas separator. However, if they must be deployed after the leak starts and the escaping gas is afire, it is very difficult and dangerous to safely move them into position through the hot gas flare.
Typical known devices of the inverted cup type are exemplified by U.S. Pat. Nos. 3,500,841 to Logan; 3,658,181 to Blair; 3,666,100 to Madij; 3,667,605 to Ziedlenski; and 3,745,773 to Cunningham.
It is the object of this invention to provide a barge-mounted oil-containment and recovery apparatus that can be safely towed into position over an oil leak in the presence of flaming gas at the surface of the water.